Selected Quarterly Consolidated Financial Information (Unaudited) - Selected Quarterly Financial Data Consolidated Financial Statements (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]                      
Interest and dividend income $ 25,213 $ 24,320 $ 23,255 $ 22,416 $ 22,183 $ 21,181 $ 20,968 $ 20,637 $ 95,204 $ 84,969 $ 78,812
Interest expense 5,186 5,223 4,936 4,790 4,844 4,742 4,573 4,786 20,135 18,945 20,972
Net interest income 20,027 19,097 18,319 17,626 17,339 16,439 16,395 15,851 75,069 66,024 57,840
Provision for loan losses 1,840 151 3,219 1,260 2,803 2,344 2,170 1,264 6,470 8,581 3,663
Net interest income, after provision for loan losses 18,187 18,946 15,100 16,366 14,536 14,095 14,225 14,587 68,599 57,443 54,177
Non-interest income 5,101 5,234 4,720 4,361 4,169 4,539 8,660 3,893 19,416 21,261 15,388
Non-interest expenses 17,041 15,587 15,595 16,292 15,517 14,366 14,799 15,266 64,515 59,948 50,994
Income before income taxes 6,247 8,593 4,225 4,435 3,188 4,268 8,086 3,214      
Provision for income taxes 2,232 3,272 1,200 1,367 1,079 1,554 2,639 1,058 8,071 6,330 6,601
Net income $ 4,015 $ 5,321 $ 3,025 $ 3,068 $ 2,109 $ 2,714 $ 5,447 $ 2,156 $ 15,429 $ 12,426 $ 11,970
Income per share:                      
Basic $ 0.19 $ 0.25 $ 0.14 $ 0.14 $ 0.10 $ 0.13 $ 0.25 $ 0.10 $ 0.71 $ 0.57 $ 0.55
Diluted $ 0.18 $ 0.24 $ 0.14 $ 0.14 $ 0.10 $ 0.12 $ 0.25 $ 0.10 $ 0.70 $ 0.57 $ 0.55
Weighted average shares:                      
Basic 21,628,168 21,632,828 21,649,423 21,639,122 21,617,801 21,606,540 21,630,660 21,662,471 21,637,344 21,629,668 21,805,143
Diluted 22,035,664 22,000,504 21,962,628 21,952,607 21,925,933 21,871,578 21,808,507 21,826,307 21,987,809 21,858,381 21,931,863